You could use Walmart oil and if it didn’t blow up would you call it good oil?
Amsoil is decent oil. I'm sure Walmart oil is OK, I've never seen an oil rig with Walmart on it so that oil probably comes from the same batch as all the rest. A dead dinosaur is a dead dinosaur...
I knew a guy who never changed the oil in any of his power equipment, as it went low in oil, he'd just top it up...he could kill every mosquito in a 2 mile radius with his lawn mower.